International Patent application publication no. WO 2006/109022 describes a method for placing an acetabular implant, such as an acetabular cup, based on the position of a plane defined by the transverse acetabular ligament (TAL) and the labrum of the acetabulum. A computer assisted surgery (CAS) approach using a trackable pointer is described together with an instrument for a non-CAS approach. However, the CAS approach and instrument based approach may not be convenient where space is at a premium or where it is not easy to identify the TAL and labrum using a trackable pointer.
There is therefore a need for a simply way of guiding or planning the positioning of an acetabular cup implant.